Pressure responsive control device for hydraulic apparatus



1955 o. NUBLING 2,721,541

RESPONSIVE CONTROL PRESS DEVICE 0 HYDRAULIC APPARATUS v Filed y 16, 1951 s Sheets-Sheet 1 FIGI FLUlD CIRCULATION FLUID PRESSURE FLUID CIRCULATION FLUID PRESSURE TORQUE INVENTOR OTTO NUBLING Oct. 25, 1955 o. NUBLING 2,721,541

PRESSURE RESPONSIVE CONTROL DEVICE FOR HYDRAULIC APPARATUS File y 6. 951 s Sheets-Sheet 2 IN VENTOR OTTO NUBLING BY WRM Oct. 25, 1955 Q NUBLING 2,721,541

PRE RE RESPONSIVE CONTRO EVICE OR HYDRAULIC APPARAT Filed May 16, 1951 3 Sheets-Sheet 3 INVENTOR OTTO NUBLING W A. M

United States Patent PRESSURE RESPONSHVE CGNTROL DEVICE FOR HYDRAULIC APPARATUS Otto Niibling, Berlin-Frohnau, Germany, assignor to Theodor Klatte, Bremen-Huchting, Germany Application May 16, 1951, Serial No. 226,563

Claims priority, application Germany May 20, 1950 7 Claims. (Cl. 121-53) This invention relates to improvements of hydraulic drives, and more particularly to a control device for regulating the effective capacity of a hydraulic apparatus.

It is an object of the present invention to provide a device by which the effective volume of a hydraulic apparatus is varied in accordance with the fluid pressure in the apparatus.

It is another object of the present invention to provide a device by which the amount of fluid circulating in a hydraulic apparatus at a predetermined number of revolutions is reduced permitting a reduction in the size of the hydraulic apparatus.

It is still another object of the present invention to provide a device by which the efficiency of a hydraulic apparatus is improved by reducing the amount of circulating fluid so as to decrease flow and leakage losses.

With these objects in view the present invention mainly consists in a hydraulic apparatus which comprises, in combination, a pair of rotary meshing gears mounted in a casing and having parallel spaced axes; a control valve including inlet conduit means provided with a supply port and with an outlet conduit means provided with a discharge port; actuating means for turning the control valve; a hollow shaft located in a bore extending in axial direction in the control valve; movable pressure responsive means mounted in the interior of the hollow shaft; and motion-transmitting means connecting the pressure responsive means with the actuating means.

The meshing gears define in the casing a working space of constant volume and consisting of a suction chamber located on one side of a plane of symmetry through the axes of the meshing gears, and of a pressure chamber located on the other side of the plane of symmetry.

The control valve is arranged turnable in one of the rotary gears in an axially extending inner chamber which is connected by duets with the suction chamber and with the pressure chamber, respectively. The actuating means turn the control valve between a maximum pumping position in which the supply and discharge ports are located on opposite sides of the plane of symmetry defined by the axes of the meshing gears and a minimum pumping position in which the supply port and the discharge port are located on both sides of the plane of symmetry and establish communication between the pressure chamber and the suction chamber for idle circulation of an operating liquid. The movable pressure responsive means communicate through conduit means in the hollow shaft and through a passage in the control valve with the inlet conduit means so as to be actuated by pressure changes. In the above described arrangement the control valve is actuated by the actuating means in accordance with pressure changes sensed by the pressure responsive means to control the effective capacity of the hydraulic apparatus in accordance with the pressure therein. Preferably, the motion transmitting means include a hydraulic servo motor.

A preferred embodiment of the present invention comprises a hollow shaft formed with at least one peripheral groove in its outer surface and at least one passage connecting the groove and the interior of the hollow shaft, rotatable means mounted on the hollow shaft and formed with a plurality of entrance ports, and further formed with a plurality of discharge ports, turnably mounted valve means located in the hydraulic apparatus and having an elongated fluid inlet and an elongated fluid outlet port arranged within the rotatable means movable over the entrance and discharge ports for varying the effective capacity of the hydraulic apparatus, the valve means formed with a bore passing therethrough and connecting the groove with the inlet port, cylinder and piston means mounted in the interior of the hollow shaft of the apparatus and communicating with the hydraulic fluid through the bore, the peripheral groove, and the passage, spring means interconnecting the cylinder and piston of the cylinder and piston means for urging the piston in one direction with respect to the cylinder, the fluid communicating with the cylinder and piston means urging the piston to move in a direction opposite to the one direction, rack means mounted in the shaft and operatively connected to the cylinder and piston means so as to move with the piston, and gear means mounted on the shaft and interconnecting the rack means and the turnable valve means whereby the turnable valve means is turned through an angle depending on the pressure of the hydraulic fluid in the apparatus.

In hydraulic drives with a fluid pump and a fluid engine arranged for continuous (i. e. stepless) torque variation, it is known to control continuously the quantity of oil circulating in unit time by varying the effective capacity, either the engine or the pump, for example by means of a centrifugal governor. If the speed of rotation of this machine and the power output of the other machine are to remain constant, then at the limits of the regulable range the latter works either with a low fluid velocity at a low speed of rotation and a large torque, or with a high fluid velocity at a high speed of rotation and a small torque.

With the Wide regulable range often required, this has disadvantages with regard to the size of the assembly and to its efliciency.

The size of the machine, the effective capacity of which is not varied, is determined by the maximum amount of fluid circulation. A wide regulable range results in a considerable size of the machine and increases the constructional costs of the apparatus;

The efliciency of the assembly, however, is lowered at the two limits of regulation due to flow losses in the conduits at maximum fluid circulation and due to leakage losses at maximum fluid pressure. According to the invention these disadvantages are eliminated in that the machine is provided with a regulating device dependent on the fiuid pressure and controlling the effective capacity of the machine.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. l is a graph showing the fluid circulation, the fluid pressure and the torque plotted against the number of revolutions of the hydraulic apparatus;

Fig. 2 is a partly cross-sectional view through a hydraulic engine on line IIII;

Fig. 3 is a longitudinal sectional view through the hydraulic engine shown in Fig. 1;

Fig. 4 is a cross-sectional view through the hydraulic engine on the line IIIIII; and

Fig. is a cross-sectional view through a hydraulic engine on line IIIIII, showing another position of the control valve.

Referring now to the drawings, the fluid conveyed by the pump is led into and out of the engine through passages 1 and 2, respectively. The fluid passes through ports 3 and 4 into working chambers 5 and 6 and drives the rotatable gear wheels 7 and 8- of the engine. These wheels are mounted on the stationary shaft 12 by means of bearings 9, and 11. The wheel 8 in the example shown is connected to a cable drum 13 which for example drives a hoisting apparatus. The present invention is not concerned with the constructional details of the engine. The fluid is led from the passages 1 and 2 through grooves 14 and 15, a non-return valve 16 and a channel 17 to cylinder and piston means. In the case of reversible engines two non-return valves 16 are provided, each of which is connected with one of the passages 1 or 2 so that regardless of the direction of rotation of the engine, the fluid pressure can still act on the stepped piston 18. The annular spaces 19 and the bore 33 are connected with the pressure side of the engine and accordingly urge the piston in one direction, and the regulator spring 20 acts in an opposite direction. At high fluid pressure, the piston is pressed against the nut 21, while the spring tension may be adjusted by means of the screw bolt 22. When the pressure drops the spring 20 is relieved and therefore moves the slide 23. The latter controls the conduits of a servomotor, known per se. The piston 25 of the servomotor carries at one end a rackbar 26. The latter acts through gear wheels 27, 28 and 29 on the control valve 30. In order to allow the control valve to turn, the fluid is led through short hoses to the passages 1 and 2 which turn with the control valve. The whole pressure responsive regulating device 31 is mounted in the stationary shaft 12 and is readily accessible after removal of the cap 34. Fluid from the servomotor, and fluid leaking from the piston 18 flows through bores 35 and through non-return valves, not shown in the drawing, back into one of the two oil passages 1 or 2.

The operation of the valve 30 is shown in Figs. 4 and 5. The chambers 36 and 37 forming elongated inlet and outlet ports communicate with the inlet and outlet passages 1 and 2. When valve 30 is turned by the gears 28 and 29, the chambers 36 and 37 are turning therewith as shown in Fig. 5. Consequently, the fluid pressed out of chamber 38 is sucked into chamber 39, and the fluid pressed out of chamber 40 is sucked into chamber 41. Only chambers 42 receive fluid from the fluid inlet, so that the amount of circulating fluid is reduced for the same number of revolutions of the rotatable means 7 and 8.

In the event that by means of a three-way valve, not shown in the drawings, the flow of fluid is reversed, chamber 37 receives fluid under pressure and the fluid is discharged through chamber 36, and, consequently, the rotatable means turn in an opposite direction.

If the hydraulic apparatus is of the reversible type, two non-return valves 16 are required, one of which is communicating through the peripheral groove with the chamber 36, and the other through the peripheral groove 14 with the chamber 37. The result of this arrangement is that regardless whether the pressure fluid is led into chamber 36 or 37, channel 17 is supplied with pressure fluid. From chamber 37 pressure fluid flows through a bore 43 into the groove 14, and from chamber 36 through bore 44 into groove 15.

In order to maintain the connection to' channel 17 in any position of valve 30, the grooves 14 and 15 extend circumferentially around the shaft 12 through an angle 4 which is larger than the maximum angle through which the valve 30 is turned.

Fig. 2 shows a hydraulic apparatus which is intended to rotate only in one direction. Consequently, only one groove 15 is provided through which the pressure fluid flows through the bore 45 to the channel 17. The nonreturn valve 16 can be omitted in this embodiment.

Fig. 1 shows in the form of a graph the results obtained with the above-described regulating device. The fluid pressure regulation begins to be effective at the ordinate marked A.

The dotted lines show how the fluid circulation increases and the torque falls in an apparatus not provided with the regulating device of the invention. The corresponding full lines show the values of fluid circulation and fluid pressure at an increasing number of revolutions of the engine in an apparatus controlled according to the invention. It will be noted that in this case the fluid circulation at a high number of revolution is only a fraction of the circulation in unregulated assemblies.

Consequently the dimensions of the whole apparatus are considerably smaller and for this reason the leakage losses in the range of maximum pressure are reduced, the flow losses are smaller because of the smaller circulation and the efliciency of the apparatus is consequently substantially increased.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of hydraulic apparatus differing from the types described above.

While the invention has been illustrated and described as embodied in a control device for hydraulic drives, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a hydraulic apparatus having a fluid flowing therethrough, in combination, a hollow shaft formed with at least one peripheral groove in its outer surface and at least one passage connecting said groove and the interior of the hollow shaft; rotatable means mounted on said hollow shaft and formed with a plurality of entrance ports, and further formed with a plurality of discharge ports; turnably mounted valve means located in the hydraulic apparatus and having an elongated fluid inlet and an elongated fluid outlet port arranged within said rotatable means movable over said entrance and discharge ports for varying the effective capacity of said hydraulic apparatus, said valve means formed with a bore passing therethrough and connecting said groove with said inlet port; cylinder and piston means mounted in the interior of said hollow shaft of said apparatus and communicating with the hydraulic fluid through said bore, said peripheral groove, and said passage; spring means interconnecting the cylinder and piston of said cylinder and piston means for urging said piston in one direction with respect to the cylinder, said fluid communicating with said cylinder and piston means urging said piston to move in a direction opposite to saidone direction; rack means mounted in said shaft and operatively connectedto said cylinder and piston means so as to move with said piston; and gear means mounted on said shaft and interconnecting said rack means and said turnable valve means whereby said turnable valve means is turned through an angle depending on the pressure of the hydraulic fluid in the apparatus.

2. In a hydraulic apparatus having a fluid flowing therethrough, in combination, a hollow shaft formed with at least one peripheral groove in its outer surface and at least one passage connecting said groove and the interior of the hollow shaft; rotatable means mounted on said hollow shaft and formed with a plurality of entrance ports, and further formed with a plurality of discharge ports; turnably mounted valve means located in the hydraulic apparatus and having an elongated fluid inlet and an elongated fluid outlet port arranged within said rotatable means movable over said entrance and discharge ports for varying the effective capacity of said hydraulic apparatus, said valve means formed with a bore passing therethrough and connecting said groove with said inlet port; cylinder and piston means mounted in the interior of said hollow shaft of said apparatus and communicating with the hydraulic fluid through said bore, said peripheral groove, and said passage; spring means interconnecting the cylinder and piston of said cylinder and piston means for urging said piston in one direction with respect to the cylinder, said fluid communicating with said cylinder and piston means urging said piston to move in a direction opposite to said one direction; a servo-motor operatively connected to said piston and actuated thereby; rack means mounted in said hollow shaft and moved by said servo-motor; and gear means mounted on said shaft and interconnecting said rack means and said turnable valve means whereby said turnable valve means is turned through an angle depending on the pressure of the hydraulic fluid in the apparatus.

3. In a hydraulic apparatus having a fluid flowing therethrough, in combination, a hollow shaft formed with a conduit means connecting the outer surface thereof with the interior thereof; rotatable means rotatably mounted on said shaft and formed with a plurality of entrance ports and with a plurality of discharge ports; valve means located in the hydraulic apparatus and movably mounted on said outer surface of said hollow shaft and having a fluid inlet port and a fluid outlet port arranged within said rotatable means movable over said entrance and discharge ports for varying the eflective capacity of the hydraulic apparatus, said valve means being formed with a passage passing therethrough and connecting said conduit means with said inlet port; hydraulic pressure responsive means mounted in the interior of said hollow shaft and communicating through said conduit means and said passage with the fluid flowing through said inlet port, said hydraulic pressure responsive means including a movable member adapted to be actuated by changes in the pressure of the fluid passing through said inlet port; and motion transmitting means interconnecting said movable member of said pressure responsive means and said movably mounted valve means so that said movable valve means is moved to control the effective capacity of the hydraulic apparatus in accordance with the hydraulic pressure in the same.

4. In a hydraulic apparatus having a fluid flowing therethrough, in combination, a hollow shaft formed with a conduit means connecting the outer surface thereof with the interior thereof; rotatable means rotatably mounted on said shaft and formed with a plurality of entrance ports and with a plurality of discharge ports; valve means located in the hydraulic apparatus and movably mounted on said outer surface of said hollow shaft and having a fluid inlet port and a fluid outlet port arranged within said rotatable means movable over said entrance and discharge ports for varying the eifective capacity of the hydraulic apparatus, said valve means being formed with a passage passing therethrough and connecting said conduit means with said inlet port; hydraulic pressure responsive means mounted in the interior of said hollow shaft and communicating through said conduit means and said passage with the fluid flowing through said inlet port, said hydraulic pressure responsive means including a movable member adapted to be actuated by changes in the pressure of the fluid passing through said inlet port; and motion transmitting means including a servo-motor and interconnecting said movable member of said pressure responsive means and said movably mounted valve means so that said movable valve means is moved to control the effective capacity of the hydraulic apparatus in accordance with the hydraulic pressure in the same.

5. In a hydraulic apparatus having a fluid flowing therethrough, in combination, a hollow shaft formed with a conduit means connecting the outer surface thereof with the interior thereof; rotatable means rotatably mounted on said shaft and formed with a plurality of entrance ports and with a plurality of discharge ports; valve means located in the hydraulic apparatus and turnably mounted on said outer surface of said hollow shaft and having a fluid inlet port and a fluid outlet port arranged within said rotatable means movable over said entrance and discharge ports for varying the effective capacity of the hydraulic apparatus, said valve means being formed with a passage passing therethrough and connecting said conduit means with said inlet port; cylinder means mounted in the interior of said hollow shaft and communicating through said conduit means in said shaft, and through said passage in said valve means with the fluid flowing through said inlet port; piston means movably mounted in said cylinder means; spring means urging said piston means in one direction to move in said cylinder means, said fluid urging said piston to move in a direction opposite to said one direction; and motion transmitting means interconnecting said piston means and said valve means so that said valve means is turned to control the effective capacity of the hydraulic apparatus in accordance with the hydraulic pressure in the same.

6. In a hydraulic apparatus, in combination a casing; a pair of rotary meshing gears mounted in said casing and having parallel spaced axes, said meshing gears defining in said casing a working space of constant volume and consisting of suction chamber means located on the one side of a plane of symmetry through the axes of said meshing gears, and pressure chamber means located on the other side of said plane of symmetry, one of said rotary gears being formed with an axially extending inner chamber, and with ducts connecting said inner chamber with said suction chamber means and said pressure chamber means, respectively; a control valve turnable in said inner chamber and including inlet conduit means provided with a supply port, and an outlet conduit means provided with a discharge port, said supply and discharge ports being located opposite said ducts; actuating means for turning said control valve between a maximum pumping position in which said supply and discharge ports are located on opposite sides of said plane of symmetry, and a minimum pumping position in which both said supply port and said discharge port are located on both sides of said plane of symmetry and establish communication between said pressure and suction chamber means for idle circulation of an operating liquid, said control valve having an axially extending bore and being formed with a passage connecting said bore with said inlet conduit means; a hollow shaft located in said bore and formed with conduit means connecting the interior thereof with said bore for communication with said inlet conduit means; movable pressure responsive means mounted in the interior of said hollow shaft and communicating through said conduit means and said passage with said inlet conduit means so as to be actuated by changes of the pressure in the same; and motion transmitting means connecting said pressure responsive means with said actuating means so that said control valve is actuated by saidpressure responsive means to control the effective capacity of the hydraulic apparatus in accordance with the pressure therein.

7'. An arrangement as claimed in claim 6 wherein saidmotion transmitting means include a hydraulic servomotor.

References Cited in the file of this patent UNITED- STATES' PATENTS Rawlings July 25, 1893 Gollirigs June 1, 1920 Seaholm Feb. 24, 1931 Demarest Oct. 2, 1934 Ljungstrom Dec. 13, 1938 Thomas et al May 6, 1941 Tucker May 6, 1947 

